Transformer



1945- s. H. M. DODINGTON 2,383,475

TRANSFORMER Filed July 18, 1942 INVENTOR .SVEN H. M DOOM 670A ATTORNEY ments.

Patented Aug. 28, 1945 TRANSFORLIER Sven H. M. Dodington,

Forest Hills, N. Y., assignor to Federal Telephone and Radio Corporation,

a corporation of Delaware Application July 18, 1942, Serial No. 451,466 4 Claims. (Cl. 178-44) This invention relates to transformers and one of the objects of the invention is to provide an improved, wide band, intermediate frequency transformer particularly adapted for tuned coupling P rposes.

Another object of the invention is to provide a wide band, intermediate frequency transformer in which the primary and secondary coils thereof are tightly coupled and yet independently tunable by magnetic means wherein the tuning of one of the coils has substantially no efl'ect upon the other.

Another object of the invention is to provide a wide band transformer wherein the primary and secondary coils thereof may be physically separated a considerable distance and yet be tightly coupled.

Still another object of the invention is to provide an improved, wide band, intermediate frequency transformer wherein the need of direct current isolating condensers and/or variable tuning condensers are eliminated.

A further object of the invention is to provide an improved, wide band, intermediate frequency transformer having a For wide band coupling transformers it is recognized that "tight coupling between the primary and secondary coils is necessary. In prior coupling transformers, however, this could only be had by using variable condensers or by omitting altogether the tuning feature. In the prior transformers, it was also necessary to closely associate the primary and secondar coils in order to obtain tight coupling. In accordance with my invention, I provide a coupling transformer in which the wide band range at intermediate and higher frequencies is maintained and this is accomplished with the elimination of the variable and direct current isolating and tuning condensers which have a reducing effect on the citcuit gain for a given band width.

More particularly, I provide individual magnetic tuning for the primary and secondary coils. To avoid affecting the tuned condition of one of the coils when the other is being tuned, I separate the two coils so that they have substantially no mutual inductance. In this relation, the two coils may be provided with magnetic tuning means suitable for transformer tuning for use on the intermediate and high frequencies without the tuning of one of the coils affecting the tuned condition of the other. In order to obtain tight coupling of the separated coils I provide a coupling link, the coils of plurality of tuning adjustthe primary coil II.

which may be wound about 5 the primary and secondary coils or they may be mounted on members adjustable relative to such coils. In this way, I not only provide independent tuning for the primary and secondary coils, but also provide for varying the tightness of the coupling.

For a better understanding of my invention, reference may be had to the following detailed description to be read in connection with the accompanying drawing, in which,

Fig. 1 is a schematic illustration of the intermediate frequency transformer of my invention coupling two parts of a circuit; and

Fig. 2 is a view in side elevation of the transformer with parts shown in section.

Referring to Fig. 1 of the drawing, the trans former of my invention comprises apart I0 having a primary coil I l and a part i2 having asecondary coil I3, the two parts ill and I2 being separatable so that the coils threof may have substantially no mutual inductance. The two parts l0 and I2 are shown in 1, for purpose of illustration, coupling two parts A and B of a circuit. The parts A and B n" "y comprise parts of any circuit wherein-it is desirable to couple them by means of a tunable transformer. As fragmentarily shown, parts A and B are two stages of an amplifler.

To couple the separated primary and secondary coils II and I3, I provide the parts ill and I: with a coupling link 20, the parts l0 and I! having link coils 2i and 23, respectively. The two link coils are connected together by a loop circuit 26, one side of which may be grounded as at 28. The lines 26 may be of any suitable length depending upon the separation of the two parts l0 and i2.

Since the two parts i0 and i2 may be identical in construction except, of course, for the number of turns for the coils I l and IS, the description of one of the parts will sufllce. As shown in Fig. 2, the part i0 comprises a hollow cylinder 30 mounted on a base 32 and around which is wound Disposed within the cylinder 30 is a composition core or plunger 3| having powdered iron as an ingredient. The core, however, may be made of any other suitable paramagnetic substance as may be desired. The core is so disposed as to be movable axially of the cylinder 30 by means of a screw 33 rigidly fixed to the core and extending through the base 32. g

The link coil H is wound adjacent the primary coil on a hollow cylinder 34, the link winding 2| being adjustable with respect to the primary coil I i by means of a screw upper end of cylinder 34 38 rotatably secured to and extending through a casing 40 surrounding the cylinders 30 and II threadably or otherwise mounted on the base 32. The cylinder 34 is shown larger in diameter than cylinder 30 so that it may be adjusted in telescoping manner about the cylinder 30. To assist the screw 36 to maintain the cylinders in adjusted relation, a collar 31 may be provided on the cylinder 30 for sliding engagement with the inner surface of the cylinder 34.

The relation of the cylinders 30 and 34 may be different, that is, the cylinder 34 may be smaller in diameter for telescoping reception within the cylinder 30 or it may be of the same size and be arranged for coaxial movement relative to the cylinder 30. Any one of these arrangements may be used to vary the tightness of coupling between the coils II and 2|. If desired, this adjustment feature may be omitted and the coil 2| wound directly over the coil H.

The part I2 of my transformer as hereinbefore stated is of substantially the same construction as the part Hi, the link coil 23 being arranged for adjustment by a screw 46 relative to the secondary coil [3. A suitable paramagnetic core similar to the core 31 is movable coaxially of the secondary coil H by a screw 43.

The loop conductors 25 of the coupling link 20 extend through openings 42 in the casings of the two parts and may be lead about other equipment on the chassis, thereby enabling the parts l and i2 to be separated and mounted in the most advantageous locations. One of the conductors 25 of the link 20 is preferably grounded as indicated at 28 to reduce undesirable capacity efiects between the individual windings of the two parts I!) and I2.

In operation, the primary winding H may be independently tuned by moving the paramagnetic core 3| co-axially within the cylinder 30 by turning the screw 33. Likewise the secondary 22 may be independently tuned by turning the screw 43.

The degree of coupling may be adjusted by moving the link coils 2| and 23 co-axially with relation to the primary and secondary windings, thus providing a third and fourth tuning adjustment.

From the foregoing description, it will be clear that my invention makes it possible to independently tune the primary and secondary coils of a coupling transformer by magnetic means whie at the same time permitting tight coupling. It will also be recognized that my invention makes it possible in wide band circuits to have both independent tuning and tightness of coupling; and this without the use of variable tuning condensers. For mechanical convenience. my invention also makes it possible to isolate the primary and secondary coils of the transformer with respect to each other on a radio chassis. Each transformer coil, for example, may be located close to its respective tube in the circuit without regard to physical distance to the other transformer coil thus permitting a reduction in the stray capacity to ground of the leads between the transformer and tubes. Circulating currents through any coil may also be confined to the vicinity of the tube and coil. With mutual inductance coupling by means of the coupling link 20, no direct current blocking condensers are necessary.

My invention lends itself very well to use in a circuit employing a push-pull diode. It is especially useful in circuits having an unbalanced input and a balanced output or vice versa, for example, from the last stage of an intermediate frequency amplifier to a full wave detector.

While I have only shown one form of my invention, it will be understood that it is given by way of illustration only and is not to be regarded as constituting a limitation upon the appended claims.

What I claim is:

1. In a wide-band, intermediate-frequency transformer having spaced-apart primary and secondary coils, a first pair of hollow cylinders respectively supporting said coils, a pair of bases respectively supporting said cylinders, each of said bases having a threaded opening therein coaxial with sa'id cylinders, a pair of shielding casings respectively mounted on said bases and enclosing said cylinders, each of said casings having a threaded opening therein oppositely disposed to the threaded openings of said bases, a pair of cores of paramagnetic material respectively within said cylinders, a pa r of screws receivable respectively in the threaded openings of said bases, said screws being respectively rigidly fixed to said cores so that movement of said screws will result in adjustment of said cores relative to sa d cylinders, a second pair of cylinders respectively within said casings and movable to coaxialiy surround said first pair of cylinders, a link circuit having coils adapted to variably couple said primary and secondary coils, said link coils being respectively carried by said second pair of cylinders, and a second pair of screws receivable respectively in the threaded openings of said casings, said second 85 pair of screws being respectively rotatably secured to said second pair of cylinders.

2. A coil, a hollow cylinder supporting said coil, 9. base supporting said hollow cylinder, a shielding casing enclosing said coil and supported by 40 said base, said casing and said base each having a threaded opening therein substantially coaxial with said cylinder, a core of paramagnetic material longitudinally movable within said coil, a screw receivable by the opening in said base, said screw being rigidly fixed to said core, a second cylinder coaxially surrounding said first-mentioned cylinder, a coil on said second cylinder, and a second screw rotatably secured to said second cylinder and receivable by the threaded opening in said casing.

3. A coil, a hollow cylinder supporting said coil, a base supporting said hollow cylinder, a casing enclosing said coil and supported on said base, a core of paramagnetic material movable within said coil, means extending from said base for moving said core, a second cylinder coaxially surrounding said first-mentioned cylinder,a coil on said second cylinder, and means extending from the casing for moving said second cylinder relative to said first cylinder.

4. A coil, a hollow cylinder supporting said coll, a base supporting said hollow cylinder, a shielding casing enclosing said coil and supported on said base, a core of paramagnetic material longitudinally movable within said coil, means extending from said base for moving said core, a second cylinder coaxially surrounding said first-mentioned cylinder, a coil on said second cylinder, and means extending from the casing for moving said second cylinder relative to said first cylinder.

SVEN H. M. DODINGTON. 

